Age-related macular degeneration (AMD) is the leading cause of blindness among adults in the United States and several Western countries. Approximately 90% of the blindness is attributable to the neovascular form of AMD and the remainder is attributable to pigment epithelial detachment and geographic atrophy. The Macular Photocoagulation Study has shown that laser treatment is effective in reducing the extent of vision loss in eyes with neovascular AMD. However, most lesions are not amenable to laser treatment and even with treatment visual acuity deteriorates to an average of 20/250 to 20/320. There are no other proven treatments for the advance forms of AMD. Prevention of vision loss from the advanced forms of AMD would have profound public health implications. If an intervention were only 30% effective in preventing choroidal neovascularization (CNV) within the high-risk population, the rate of legal blindness from AMD could be cut in half. The presence of large drusen in the macula is a strong predictor of the development of CNV. Low intensity laser treatment causes high-risk drusen to disappear in most eyes. Controlled, pilot, clinical trials on the effect of laser treatment on development of CNV and loss of vision are underway on two groups of patients: patients with bilateral large drusen and patients with unilateral CNV and the second (fellow) eye with large drusen. Initial reports provide evidence of an increased rate of CNV in treatment fellow eyes, at lest for the first year after treatment. For eyes of patients with bilateral drusen, two small clinical trials show evidence of decreased CNV and better vision in treated eyes at 3 years and one large trial shows little difference between treated and untreated eyes through 18 months. The large segment of the population that might benefit, or be harmed, by laser treatment mandates a thorough evaluation of the treatment. We propose the Complications of Age-related Macular Degeneration Prevention Trial (CAPT) to assess the safety and effectiveness of laser treatment in preventing loss of vision among patients with bilateral drusen. Change in visual acuity will be the primary outcome variable. Secondary outcome measures will be the incidence of CNV, pigment epithelial detachment and geographic atrophy, change in contrast threshold, and change in critical point size for reading. In addition, the participating patients will be described with by their scores on both general and vision specific quality of life assessments.